Insect Growth Disruptors Cause Mouthpart Malformations, Inhibition of Feeding, and Mortality in the Neotropical Brown Stink Bug Euschistus heros (Hemiptera: Pentatomidae)

Abstract

The Neotropical brown stink bug, Euschistus heros, is the most important sucking pest of soybean crops, quantitatively and qualitatively affecting grain and seed. This study aimed to determine mouthpart deformities, feeding inhibition, and E. heros nymphs’ mortality when in contact with insect growth disruptors (IGDs). The effects of two insecticides of the chitin biosynthesis inhibitor group (CBIs), lufenuron and diflubenzuron, and the juvenile hormone analog pyriproxyfen were tested in the laboratory. CBI application promoted mouthpart deformities, feeding inhibition, alteration of metamorphosis, and mortality of E. heros nymphs. Although pyriproxyfen did not cause mouthpart deformation, it caused certain mortality for nymphs, possibly due to physiological disorders. Lufenuron caused feed inhibition and mortality in less time when compared with diflubenzuron and pyriproxyfen. It was also more toxic to 4th instar nymphs. The insecticides, when used in higher concentrations, increased nymph’s mortality in less time. Nymphs with deformed mouthparts were unable to feed and died. All IGDs in the tested concentrations caused 100% mortality and prevented adult formation.